8 Western Energy Imbalance Market
On November 1, 2014, the California Independent System Operator Corporation (CAISO) and Portland based PacifiCorp fully activated the Western Energy Imbalance Market (WEIM). This real-time market is the first of its kind in the West. The WEIM allows balancing authorities outside of the CAISO balancing authority area to voluntarily take part in the imbalance energy portion of the CAISO locational marginal price-based real-time market. PacifiCorp, the CAISO, and market participants participated in market simulations prior to the start of the Energy Imbalance Market on November 1, including parallel production from October 1 to November 1.
The WEIM uses state-of-the-art software to analyze regional grid needs and make available low-cost generation to meet demand every five minutes. It can bring many benefits to the West such as cost savings, improving the efficiency of dispatching resources, facilitating the renewable integration, more reliability, etc.
On December 1, 2015, NV Energy (NVE), the Nevada-based utility successfully began participating in the WEIM. With the addition of NV Energy (NVE), the WEIM expanded into Nevada, where the utility serves 2.4 million customers.
On October 1, 2016, Phoenix-based Arizona Public Service (AZPS) and Puget Sound Energy (PSEI) of Washington State successfully began full participation in the WEIM. With the addition of AZPS and PSEI, the WEIM footprint grew to over 5 million consumers in California, Washington, Oregon, Arizona, Idaho, Wyoming, Nevada and Utah.
On October 1, 2017, Portland General Electric Company (PGE) became the fifth western utility to successfully begin full participation in the WEIM. PGE joined AZPS, PSEI, NVE, PacifiCorp and the ISO, together serving over 38 million consumers in eight states: California, Arizona, Oregon, Washington, Utah, Idaho, Wyoming and Nevada.
On April 4, 2018, Boise-based Idaho Power (IPCO) and Powerex of Vancouver (BCHA), British Columbia successfully entered the WEIM, allowing the ISO’s real-time power market to serve energy imbalances occurring within about 55 percent of the electric load in the Western Interconnection. The eight WEIM participants serve more than 42 million consumers in the power grid stretching from the border with Canada south to Arizona, and eastward to Wyoming.
On April 3, 2019, Sacramento Municipal Utility District (SMUD), part of the Balancing Authority of Northern California (BANC), successfully began full participation in the WEIM, becoming the first publicly owned agency to become a WEIM entity.
On April 1, 2020, Seattle City Light (SCL) and Salt River Project (SRP) successfully joined the WEIM. The two utilities serve about 1.5 million customers in the West’s first real-time energy market. Together with SRP and SCL, the WEIM participants represent 61 percent of the load in the Western Electric Coordinating Council (WECC).
On March 25, 2021, the Turlock Irrigation District (TIDC) and the Balancing Area of Northern California (BANC) Phase 2, comprised of the Modesto Irrigation District (MID), the City of Redding, the City of Roseville, and the Western Area Power Administration – Sierra Nevada Region, began participating in the West’s first real-time energy market.
On April 1, 2021, Los Angeles Department of Water and Power (LADWP) and the Public Service Company of New Mexico (PNM) joined the WEIM. PNM’s entrance expanded the real-time energy market into New Mexico.
On June 16, 2021, NorthWestern Energy (NWMT) began participating in the WEIM. With the addition of NWMT, the WEIM footprint extended into Montana, serving consumers across ten states, including portions of Arizona, California, Idaho, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming, and Montana.
On March 2, 2022, Avista Utilities (AVA) and Tacoma Power (TPWR) became the new members of the WEIM, with both utilities serving a combined 600,000 electric customers in the Pacific Northwest.
On May 3, 2022, the Bonneville Power Administration (BPAT) and Tucson Electric Power (TEPC) both formally joined the WEIM, becoming the new participants in the WEIM. With a total of 19 participants, the WEIM serves 77% of the demand for electricity in the Western United States.
On April 5, 2023, Western Area Power Administration (WAPA) Desert Southwest region, El Paso Electric (EPE) and AVANGRID formally began participating in the WEIM, which now represents nearly 80% of the demand for electricity in the Western Interconnection.
WEIM Prices
Figure 36, Figure 37 and Figure 38 show daily simple average prices for WEIM Load Aggregation Points (ELAP) in FMM for all hours, on-peak hours and off-peak hours, respectively.
The FMM ELAP prices in May decreased from the previous month correlated with declining natural gas prices.
Figure 36: WEIM Simple Average LAP Prices (All Hours) in FMM
Figure 37: WEIM Simple Average LAP Prices (On-Peak Hours) in FMM
Figure 38: WEIM Simple Average LAP Prices (Off-Peak Hours) in FMM
Figure 39, Figure 40 and Figure 41 show daily simple average prices for WEIM LAPs (ELAP) in RTD for all hours, on-peak Hours and off-peak hours, respectively.
The RTD ELAP prices in May decreased from the previous month correlated with declining natural gas prices.
Figure 39: WEIM Simple Average LAP Prices (All Hours) in RTD
Figure 40: WEIM Simple Average LAP Prices (On-Peak Hours) in RTD
Figure 41: WEIM Simple Average LAP Prices (Off-Peak Hours) in RTD
Figure 42 shows the daily price frequency for ELAP prices above $250/MWh and below $0/MWh in FMM.
The cumulative frequency of FMM ELAP prices above $250/MWh decreased to 0.31 percent in May from 0.52 percent in the previous month. The cumulative frequency of negative FMM ELAP prices jumped to 87.00 percent in May from 22.71 percent in the previous month.
Figure 42: Daily Frequency of WEIM LAP Positive Price Spikes and Negative Prices in FMM
Figure 43 shows the daily price frequency for ELAP prices above $250/MWh and below $0/MWh in RTD.
The cumulative frequency of RTD ELAP prices above $250/MWh decreased to 0.24 percent from 0.26 percent in the previous month. The cumulative frequency of RTD ELAP negative prices jumped to 22.22 percent in May from 7.57 percent in the previous month.
Figure 43: Daily Frequency of WEIM LAP Positive Price Spikes and Negative Prices in RTD
WEIM Transfers
The following figures show the daily volume of WEIM transfers for each WEIM entity in FMM. IMPORT represents the total WEIM transfers from other BAAs. EXPORT represents the total WEIM transfers out to other BAAs.
Figure 44 shows the daily volume of WEIM transfers for CAISO in FMM. Figure 45 shows the daily volume of WEIM transfers for AVA in FMM. Figure 46 shows the daily volume of WEIM transfers for AVRN in FMM. Figure 47 shows the daily volume of WEIM transfers for AZPS in FMM. Figure 48 shows the daily volume of WEIM transfers for BANC in FMM. Figure 49 shows the daily volume of WEIM transfers for BCHA in FMM. Figure 50 shows the daily volume of WEIM transfers for BPA in FMM. Figure 51 shows the daily volume of WEIM transfers for EPE in FMM. Figure 52 shows the daily volume of WEIM transfers for IPCO in FMM. Figure 53 shows the daily volume of WEIM transfers for LADWP in FMM. Figure 54 shows the daily volume of WEIM transfers for NEVP in FMM. Figure 55 shows the daily volume of WEIM transfers for NWMT in FMM. Figure 56 shows the daily volume of WEIM transfers for PACE in FMM. Figure 57 shows the daily volume of WEIM transfers for PACW in FMM. Figure 58 shows the daily volume of WEIM transfers for PGE in FMM. Figure 59 shows the daily volume of WEIM transfers for PNM in FMM. Figure 60 shows the daily volume of WEIM transfers for PSEI in FMM. Figure 61 shows the daily volume of WEIM transfers for SCL in FMM. Figure 62 shows the daily volume of WEIM transfers for SRP in FMM. Figure 63 shows the daily volume of WEIM transfers for TEP in FMM. Figure 64 shows the daily volume of WEIM transfers for TID in FMM. Figure 65 shows the daily volume of WEIM transfers for TPWR in FMM. Figure 66 shows the daily volume of WEIM transfers for WALC in FMM.
Figure 44: WEIM Transfers for CAISO in FMM
Figure 45: WEIM Transfers for AVA in FMM
Figure 46: WEIM Transfers for AVRN in FMM
Figure 47: WEIM Transfers for AZPS in FMM
Figure 48: WEIM Transfers for BANC in FMM
Figure 49: WEIM Transfers for BCHA in FMM
Figure 50: WEIM Transfers for BPAT in FMM
Figure 51: WEIM Transfers for EPE in FMM
Figure 52: WEIM Transfers for IPCO in FMM
Figure 53: WEIM Transfers for LADWP in FMM
Figure 54: WEIM Transfers for NEVP in FMM
Figure 55: WEIM Transfers for NWMT in FMM
Figure 56: WEIM Transfers for PACE in FMM
Figure 57: WEIM Transfers for PACW in FMM
Figure 58: WEIM Transfers for PGE in FMM
Figure 59: WEIM Transfers for PNM in FMM
Figure 60: WEIM Transfers for PSEI in FMM
Figure 61: WEIM Transfers for SCL in FMM
Figure 62: WEIM Transfers for SRP in FMM
Figure 63: WEIM Transfers for TEPC in FMM
Figure 64: WEIM Transfers for TIDC in FMM
Figure 65: WEIM Transfers for TPWR in FMM
Figure 66: WEIM Transfers for WALC in FMM
The following figures show the daily volume of WEIM transfers for each WEIM entity in RTD. IMPORT represents the total WEIM transfers from other BAAs. EXPORT represents the total WEIM transfers out to other BAAs.
Figure 67 shows the daily volume of WEIM transfers for CAISO in RTD. Figure 68 shows the daily volume of WEIM transfers for AVA in RTD. Figure 69 shows the daily volume of WEIM transfers for AVRN in RTD. Figure 70 shows the daily volume of WEIM transfers for AZPS in RTD. Figure 71 shows the daily volume of WEIM transfers for BANC in RTD. Figure 72 shows the daily volume of WEIM transfers for BCHA in RTD. Figure 73 shows the daily volume of WEIM transfers for BPA in RTD. Figure 74 shows the daily volume of WEIM transfers for EPE in RTD. Figure 75 shows the daily volume of WEIM transfers for IPCO in RTD. Figure 76 shows the daily volume of WEIM transfers for LADWP in RTD. Figure 77 shows the daily volume of WEIM transfers for NEVP in RTD. Figure 78 shows the daily volume of WEIM transfers for NWMT in RTD. Figure 79 shows the daily volume of WEIM transfers for PACE in RTD. Figure 80 shows the daily volume of WEIM transfers for PACW in RTD. Figure 81 shows the daily volume of WEIM transfers for PGE in RTD. Figure 83 shows the daily volume of WEIM transfers for PSEI in RTD. Figure 84 shows the daily volume of WEIM transfers for SCL in RTD. Figure 85 shows the daily volume of WEIM transfers for SRP in RTD. Figure 86 shows the daily volume of WEIM transfers for TEP in RTD. Figure 87 shows the daily volume of WEIM transfers for TID in RTD. Figure 88 shows the daily volume of WEIM transfers for TPWR in RTD. Figure 89 shows the daily volume of WEIM transfers for WALC in RTD.
Figure 67: WEIM Transfers for CAISO in RTD
Figure 68: WEIM Transfers for AVA in RTD
Figure 69: WEIM Transfers for AVRN in RTD
Figure 70: WEIM Transfers for AZPS in RTD
Figure 71: WEIM Transfers for BANC in RTD
Figure 72: WEIM Transfers for BCHA in RTD
Figure 73: WEIM Transfers for BPA in RTD
Figure 74: WEIM Transfers for EPE in RTD
Figure 75: WEIM Transfers for IPCO in RTD
Figure 76: WEIM Transfers for LADWP in RTD
Figure 77: WEIM Transfers for NEVP in RTD
Figure 78: WEIM Transfers for NWMT in RTD
Figure 79: WEIM Transfers for PACE in RTD
Figure 80: WEIM Transfers for PACW in RTD
Figure 81: WEIM Transfers for PGE in RTD
Figure 82: WEIM Transfers for PNM in RTD
Figure 83: WEIM Transfers for PSEI in RTD
Figure 84: WEIM Transfers for SCL in RTD
Figure 85: WEIM Transfers for SRP in RTD
Figure 86: WEIM Transfers for TEP in RTD
Figure 87: WEIM Transfers for TID in RTD
Figure 88: WEIM Transfers for TPWR in RTD
Figure 89: WEIM Transfers for WALC in RTD
WEIM Cost Allocation
Figure 90 shows daily real-time imbalance energy offset (RTIEO) cost for each WEIM entity and Figure 91 shows daily real-time congestion imbalance offset (RTCIO) cost for each WEIM entity. RTIEO and RTCIO are calculated as per Tariff Section 11.5.4. Since the implementation of the new market, imbalance offset is a charge allocated to measured demand. A positive value indicates a charge to measured demand and a negative value indicates a payment to measured demand.
Total RTIEO in May increased to $2.04 million from $0.99 million in the previous month. Total RTICO increased to -$13.06 million in May from -$26.62 million in the previous month.
Figure 90: WEIM Real-Time Imbalance Energy Offset by Area
Figure 91: WEIM Real-Time Congestion Imbalance Offset by Area
Figure 92 shows daily bid cost recovery for each WEIM entity.
Total BCR increased to $2.25 million in May from $1.63 million in the previous month.
Figure 92: WEIM Bid Cost Recovery by Area
Figure 93 shows the flexible ramping up uncertainty payment for each WEIM entity. Total flexible ramping up uncertainty payment in May decreased to $212,000 from $287,000 in the previous month.
Figure 94 shows the flexible ramping down uncertainty payment for each WEIM entity. Total flexible ramping down uncertainty payment in May dropped to $15,000 from $74,500 in the previous month.
Figure 95 shows the flexible ramping forecast payment for each WEIM entity. Total forecast payment in April increased to -$19,500 from -$675,000 in the previous month.
Figure 93: Flexible Ramping Up Uncertainty Payment
Figure 94: Flexible Ramping Down Uncertainty Payment
Figure 95: Flexible Ramping Forecast Payment
The ISO’s Western Energy Imbalance Market Business Practice Manual describes the methodology for determining whether a WEIM participating resource is dispatched to support transfers to serve California load. The methodology ensures that the dispatch considers the combined energy and associated marginal greenhouse gas (GHG) compliance cost based on submitted bids. The WEIM dispatches to support transfers into the ISO are documented below in Figure 96 and Table 13.
Figure 96: WEIM Transfer into ISO by Fuel Type
| Month-Year | Coal (%) | Gas (%) | Water (%) | Other Non-Emitting (%) |
|---|---|---|---|---|
| Jun-2021 | 0.1% | 0 | 58.0% | 41.9% |
| Jul-2021 | 1.1% | 0 | 63.2% | 35.7% |
| Aug-2021 | 0.5% | 0.0% | 60.8% | 38.6% |
| Sep-2021 | 0.2% | 0 | 60.5% | 39.3% |
| Oct-2021 | 1.2% | 0 | 53.0% | 45.8% |
| Nov-2021 | 0.5% | 0 | 49.0% | 50.5% |
| Dec-2021 | 0.3% | 0 | 45.9% | 53.9% |
| Jan-2022 | 0.0% | 0 | 23.4% | 76.6% |
| Feb-2022 | 0.1% | 0 | 27.8% | 72.0% |
| Mar-2022 | 0 | 0 | 15.1% | 84.9% |
| Apr-2022 | 0.2% | 0 | 30.1% | 69.7% |
| May-2022 | 0.5% | 4.8% | 25.5% | 69.3% |
| Jun-2022 | 3.3% | 15.0% | 16.4% | 65.2% |
| Jul-2022 | 3.3% | 4.7% | 32.8% | 59.2% |
| Aug-2022 | 0.2% | 3.7% | 41.2% | 54.9% |
| Sep-2022 | 0.1% | 0.8% | 50.7% | 48.4% |
| Oct-2022 | 0.0% | 3.9% | 31.2% | 64.9% |
| Nov-2022 | 0.0% | 3.4% | 34.6% | 61.9% |
| Dec-2022 | 0.1% | 2.2% | 41.2% | 56.5% |
| Jan-2023 | 1.1% | 2.1% | 40.5% | 56.4% |
| Feb-2023 | 0.1% | 4.4% | 34.3% | 61.2% |
| Mar-2023 | 0.1% | 4.9% | 26.4% | 68.6% |
| Apr-2023 | 0 | 6.2% | 24.5% | 69.3% |
| May-2023 | 0 | 16.7% | 15.0% | 68.3% |